1. Field of the Invention
The present invention relates to a method for testing a prescaler IC (integrated circuit) and a test probe card, and more specifically to a prescaler IC testing method and a test probe card, which have an AC test function and a DC test function.
2. Description of Related Art
A recent high speed and high integration IC technology is greatly expected as a key technology for constructing a high informazation society. In particular, a high speed and high integration IC such as a prescaler IC has been applied over an extremely wide field from a mobile communication to an audio visual in-home instrument. Because, use of the prescaler IC is increased because a PLL (phase locked loop) technology has been introduced into various systems.
Generally, a process for manufacturing the prescaler IC mainly includes a diffusion process, a wafer check process (conventionally called a "pellet/wafer process" (P/W process)), an assemble process, a sorting process, and a testing process. In particular, the process for checking the characteristics of the prescaler IC includes the wafer check process in which a DC characteristics and an AC characteristics is checked to the ICs in the form of a wafer, and the sorting process in which a DC test/sorting and an AC test/sorting are performed after the IC is packaged.
In these wafer check process and sorting process, the DC test and the AC test are performed by using different IC test probe cards, respectively.
Referring to FIG. 1, a diagram illustrating the probe card and the IC DC tester is shown as one conventional example. An IC DC tester 10 and an IC test probe card 11A as shown in FIG. 1 are used in the wafer check process. Contact probes (not shown) provided at tip ends of wiring patterns 22 formed on the probe card 11A are brought into contact with a prescaler IC 18 to be checked, so that the DC test is performed.
Various information is transferred between the IC DC tester 10 and the probe card 11A. First, on the basis of a test program previously set in the IC DC tester 10, various DC voltages are supplied from the IC DC tester 10 to the probe card 11A. These DC voltages are supplied through the wiring patterns 22 to the prescaler IC 18 as a power supply voltage, an input terminal voltage, etc.
Then, an output voltage is outputted from the prescaler IC 18 to the IC DC tester 10. This output voltage is examined on the basis of a non-defective/defective reference previously set in the IC DC tester 10, so that a non-defective/defective of the prescaler IC 18 is discriminated.
As mentioned above, in the wafer test process, the DC test is performed by using the probe card 11A specialized for only the DC test and having only the wiring patterns formed thereon. Incidentally, in the sorting process performed after packaged, the probe card is not used, and a sorting tool constituted of for example, an IC socket, is used.
Referring to FIG. 2, a diagram illustrating the probe card and the AC tester is shown as another conventional example. An IC AC tester 24 and an IC test probe card 11B as shown in FIG. 2 are used in the wafer check process. Contact probes (not shown) provided at tip ends of wiring patterns 22 formed on the probe card 11B are brought into contact with a prescaler IC 18 to be checked, so that the AC test is performed.
The AC tester 24 includes an AC signal source 25 and an AC testing circuit 26. The AC signal source 25 supplies AC signals to the prescaler IC 18 connected to the probe card 11B, and AC output signals obtained from the prescaler IC 18 are examined by the AC testing circuit 26, similarly to the DC test.
Also in this case, the probe card 11B has only the wiring patterns formed thereon. In addition, in the sorting process performed after packaged, the probe card is not used, and a sorting tool is used, similarly to the DC test.
In the case of using the construction shown in FIG. 1, only the DC test can be performed. As a result, ICs which are defective from the viewpoint of the AC operation but which cannot be excluded in the DC test, are supplied to a next step, namely, the assembling process in which an additional value is added.
On the other hand, in the case of using the construction shown in FIG. 2, the AC test must be performed after the wafer check (DC test) is performed using the construction shown in FIG. 1. As a result, the number of steps required in the wafer check process is increased, and an equipment for the AC test is required in the wafer check process.
In order to overcome the above mentioned problem, for example, Japanese Utility Model Application Pre-examination Publication No. Heisei 1-79837 proposed to provide a probing block for the AC test and another probing block for the DC test on a single probe card, so that different IC chips are simultaneously checked. In this proposal, however, both the IC DC tester and the AC tester are required as the testing equipment. In addition, when the test goes from the DC test to the AC test, it is necessary to move the probe card, or to move the wafer, with the result that a test time inevitably becomes long. In other words, the processing capacity drops.
Furthermore, Japanese Patent Application Pre-examination Publication No. Showa 62-123732 proposed to provide a plurality of checking circuits on the probe card. In this construction, however, the checking circuits only check the output signals from the ICs to be checked, but no attention is paid to the input signal to be supplied to the ICs to be checked. In addition, the relation of signal transfer between the testing equipment and the ICs to be checked is indefinite and therefore not practical.